Recently, hybrid electric rotary excavators have been being developed, in which a rotary body is driven by an electric motor while other members such as a work equipment and a carrier are driven by a hydraulic actuator (see, for instance, Patent Document 1).
In such electric rotary excavators, since the rotation of the rotary body is driven by the electric motor, even when the rotary body is rotated simultaneously with lifting up of a hydraulically-driven boom and arm, the rotation of the rotary body is not affected by the lifting of the boom and the arm. Accordingly, an energy loss at control valves or the like can be reduced as compared to an arrangement in which the rotary body is hydraulically driven, thereby enhancing energy efficiency.
[Patent Document 1] JP-A-2001-11897